1. Field of the Invention
The present invention relates to a control apparatus using one or a plurality of microcomputers.
2. Description of the Prior Art
Even in a conventional apparatus which could be controlled by a single microcomputer, multi functions have been recently required. To satisfy this demand, there is a tendency to use a plurality of microcomputers. Due to this, many loads can be easily controlled with a high degree of accuracy on the basis of a program. However, to realize this, it is necessary to assume that the microcomputers will operate normally. On the other hand, the use of a plurality of microcomputers causes the control to be complicated and produces a large possibility of error due to the noise generated in the apparatus, or the noise from a outside, etc. Therefore, if there occurs the difference in information among the respective microcomputers, correct control cannot be performed.
In addition, there are efforts to reduce the noise margin to realize a high processing speed and the like, resulting in an increase in the possibility of error. Under such situation, if a malfunction should occur and one of the microcomputers operates erroneously, another microcomputer controlled by this malfunctioning microcomputer will not operate correctly, if this occurs, there is a risk that the apparatus controlled by the microcomputer may become unsafe.
Particularly, although safety is important in control of the loads such as a lamp, heater and the like that may endanger humans, if the malfunction should occur, the only way to correct the problem is to reset the load from the outside.
Further, the contents of the registers in the microcomputers may be damaged due to not only the external noise such as static electricity or the like but also the internal noise or the like. The possibility of a program malfunction in the microcomputer as a result of such damage is increasing.